Switch arrangement and method for electrical switching

ABSTRACT

A switch arrangement comprises a first and a second terminal ( 1, 2 ), a first switch ( 3 ), a current sensor ( 10 ), a first and a second control circuitry ( 20, 30 ). The first switch ( 3 ) comprises a control terminal ( 4 ), a first terminal ( 5 ) which is coupled to the first terminal ( 1 ) of the switch arrangement and a second terminal ( 6 ) which is coupled to the second terminal ( 2 ) of the switch arrangement. The current sensor ( 10 ) is realized for the measurement of a load current (Iload) flowing through the first switch ( 3 ). The first control circuitry ( 20 ) is coupled to an output terminal of the current sensor ( 10 ) and to the control terminal ( 4 ) of the first switch ( 3 ). The second control circuitry ( 30 ) is coupled to the control terminal ( 4 ) of the first switch ( 3 ).

RELATED APPLICATIONS

This is a U.S. national stage under 35 USC §371 of application No.PCT/EP2007/057482, filed on Jul. 19, 2007.

This application claims the priority of European Patent Application06015236.0 filed Jul. 21, 2006, the disclosure content of which ishereby incorporated by reference.

The present invention relates to a switch arrangement and a method forelectrical switching.

BACKGROUND OF THE INVENTION

Switch arrangements can be used for connecting and disconnecting anelectrical energy source and an electrical load. Because a relay canalso fulfill the function of connecting and disconnecting two electricalcircuits, a switch arrangement sometimes is called a solid state relay.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a switch arrangement and amethod for electrical switching with a high flexibility and a currentlimitation capability.

This object is solved by a switch arrangement comprising the features ofclaim 1 and by a method for electrical switching according to claim 13.Preferred embodiments are presented in the respective dependent claims.

A switch arrangement comprises a first and a second terminal, a firstswitch, a current sensor, a first control circuitry and a second controlcircuitry. The first switch comprises a control terminal and a first anda second terminal. The first terminal of the first switch is coupled tothe first terminal of the switch arrangement. The second terminal of thefirst switch is coupled to the second terminal of the switcharrangement. The current sensor is connected in series to the firstswitch. The series circuit, comprising the first switch and the currentsensor, is arranged between the first terminal and the second terminalof the switch arrangement.

The first and the second control circuitries are each coupled to thecontrol terminal of the first switch. An output terminal of the currentsensor is coupled to the first control circuitry.

A load current flows through the first and the second terminal of theswitch arrangement and through the series circuit of the first switchand the current sensor. A signal comprising information about the loadcurrent is provided by the current sensor at the output terminal of thecurrent sensor and is received by the first control circuitry. The firstcontrol circuitry applies a first signal to the control terminal of thefirst switch and the second control circuitry supplies a second signalto the control terminal of the first switch. The first signal depends onthe load current. The second signal depends on a first mode signal for afirst state of the switch arrangement.

It is an advantage of the switch arrangement comprising the currentsensor that the first switch can be controlled using a directinformation about the load current flowing through the switch. It is anadvantage of the switch arrangement with the first control circuitryproviding the first signal that the switch can be operated in anon-state or an off-state. Therefore, the load current can be limited. Itis an advantage of the second control circuitry to which a first modesignal is provided that it allows a high flexibility in controlling thefirst switch.

In an embodiment, the first control circuitry is provided for currentlimitation of the load current by a first threshold signal. The currentlimitation is provided in such a way by the first control circuitry thatthe load current is smaller or is equal to the first threshold signal.

In an embodiment, the switch arrangement comprises a protectioncircuitry against short circuit. The protection circuitry is connectedto the output terminal of the current sensor. Further on, the protectioncircuitry couples the control terminal of the first switch to areference potential terminal. The protection circuitry advantageouslyprovides a gate voltage to the control terminal of the first switch witha value so that the first switch is switched in an off-state.

In an embodiment, the current sensor is connected between the firstswitch and the second terminal. In a preferred embodiment, the currentsensor is connected between the first terminal and the first switch.

The first and/or the second control circuitries can be realized asvoltage sources. The first and/or the second control circuitries canpreferably be realized as current sources.

In an embodiment, the first switch is realized as a bipolar transistor,comprising a base terminal as the control terminal. The first and thesecond control circuitries, therefore, can provide a base current to thebase terminal by providing the first and the second signal in the formof a first and a second current signal.

In an alternative embodiment, the first switch is realized as afield-effect transistor, abbreviated FET. The first switch can be aP-channel field-effect transistor. In a preferred embodiment, the firstswitch is a N-channel field-effect transistor.

In an embodiment, the first switch is realized as ametal-oxide-semiconductor field-effect transistor, abbreviated MOSFET.In a preferred embodiment, the first switch is realized as a powerMOSFET.

Field-effect transistors and especially MOSFETs comprise a gatecapacitance between the control terminal and a controlled section of thetransistor between the first and the second terminal of the firstswitch. An output circuit of the first switch comprises the controlledsection. A gate voltage at the control terminal of the first switch iscontrolled by the first and the second signal circuitries. It is anadvantage of this embodiment that the charge on the gate capacitance canbe controlled exactly and, therefore, the first switch can be operatedin an on-state or an off-state. In a preferred embodiment, the firstswitch can be operated in an on-state, an off-state or anintermediate-state as a controlled resistor.

The first and the second control circuitries, realized as voltagesources, can provide the first and the second signal in the form of afirst and a second voltage signal to the gate capacitance and can chargeand discharge the gate capacitance.

The first and the second control circuitries, realized as currentsources, can provide the first and the second signal in the form of afirst and a second current signal to the gate capacitance and can chargeand discharge the gate capacitance. It is an advantage of thisembodiment that the transitions between the different states can beexactly controlled.

In an embodiment, the first control circuitry provides the first signalin such a way that the load current is smaller or is equal to a firstthreshold signal. If the load current obtains a current value which isapproximately the value of the first threshold signal, the resistancebetween the first and the second terminal of the first switch can beincreased in such a way, that the load current is not increased abovethe first threshold signal. It is an advantage of a switch arrangementwith such a current limitation capability, that a load has not to bedisconnected from an energy source, if the load current rises to thevalue of the first threshold signal. The load has not to be completelyswitched off in case the load current obtains a value which isapproximately equal to the first threshold signal.

In an embodiment, the switch arrangement is designed as a high sideswitch, so that the switch arrangement is arranged between the energysource and the load.

In an embodiment, the switch arrangement is designed as a bidirectionalswitch so that the load current can flow from the first terminal of theswitch arrangement to the second terminal of the switch arrangement at afirst point in time and from the second terminal to the first terminalat a second point in time.

In an embodiment, the first switch is realized using a firstsemiconductor body. The first and the second control circuitries arerealized using a second semiconductor body which is coupled to the firstsemiconductor body. A measurement resistor of the current sensor can becoupled to the first and the second semiconductor body.

In a preferred embodiment, the switch arrangement including the firstswitch, the first and the second control circuitries is realized using acommon semiconductor body. The measurement resistor of the currentsensor can be separately realized and be coupled to the commonsemiconductor body.

According to an aspect of the invention, the method for electricalswitching comprises the following steps: A controlling of a first switchis performed by providing a first signal and/or a second signal to acontrol terminal of the first switch. The first signal is generateddepending on a load current which flows through the first switch. Thesecond signal is provided depending on a first mode signal. It is anadvantage of the method for electrical switching, that by the use of twosignals the first switch can be operated in a flexible manner.

In an embodiment, the first signal is provided in such a way that theload current is smaller or is equal to a first threshold signal.

In an embodiment, a third signal is provided to the control terminal ofthe first switch for protection against short circuit. The third signaldepends on the load current and a second threshold signal. The firstthreshold signal is advantageously smaller than the second thresholdsignal.

In a further development, the third signal can stop the load current incase the load current is higher than the second threshold signal.

In an embodiment, the second signal and the first signal are currentsignals. In a preferred embodiment, the sign of the first signal dependson the difference of the load current and a first threshold signal. Ifthe load current is smaller than the first threshold signal, the firstsignal is generated with a positive value so that the first switch isoperated in an on-state and obtains a low resistance. If the loadcurrent is greater than the first threshold signal, then the firstsignal obtains a negative value. If the load current is approximatelyequal to the first threshold signal, the first signal obtains a value ofapproximately 0.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of figures of exemplary embodiments mayfurther illustrate and explain the invention.

FIG. 1 shows a schematic of an exemplary embodiment of a switcharrangement,

FIG. 2 shows an exemplary embodiment of a second control circuitry and

FIG. 3 shows an exemplary embodiment of signals provided by the switcharrangement.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary embodiment of a switch arrangement. The switcharrangement comprises a first switch 3, a first terminal 1, a secondterminal 2, a first control circuitry 20, a second control circuitry 30,a protection circuitry 40, a current sensor 10 and a first transistor60. An electrical load 70 is connected to the second terminal 2 of theswitch arrangement. The load 70 is represented by a resistor 71 and acapacitor 72 which are connected in parallel between the second terminal2 of the switch arrangement and a reference potential terminal 8. Anenergy source 7 is connected to the first terminal 1 of the switcharrangement.

The first switch 3 comprises a first terminal 5 which is connected viathe current sensor 10 to the first terminal 1 of the switch arrangement.The first switch 3 further comprises a second terminal 6 which isconnected to the second terminal 2 of the switch arrangement.

The current sensor 10 comprises a measurement resistor 11 and anamplifier 12. The amplifier 12 has two input terminals which areconnected to the two terminals of the measurement resistor 11. Theamplifier 12 is realized as a differential amplifier. An output terminalof the amplifier 12 is connected to an output terminal of the currentsensor 10 which is connected to the first control circuitry 20 and tothe protection circuitry 40.

An output terminal of the first control circuitry 20, an output terminalof the second control circuitry 30 and an output terminal of theprotection circuitry 40 are connected to the control terminal 4 of thefirst switch 3. The first control circuitry 20 comprises an operationaltransconductance amplifier 21, abbreviated OTA, and a second switch 25.The operational transconductance amplifier 21 comprises a first inputterminal 22 and a second input terminal 23 which is connected to theoutput terminal of the current sensor 10. The operationaltransconductance amplifier 21 also comprises an output terminal 24 whichis coupled to the output terminal of the first control circuitry 20 viathe second switch 25.

The second control circuitry 30 comprises a current sink 32 and a thirdswitch 31. The current sink 32 is connected to the reference potentialterminal 8 and is coupled to the output terminal of the second controlcircuitry 30 via the third switch 31.

The protection circuitry 40 comprises a comparator 41, a logic gate 45and a fourth switch 46. The comparator 41 comprises a first inputterminal 42 which is connected to the output terminal of the currentsensor 10, a second input terminal 43 and an output terminal 44. Thelogic gate 45 has the function of an AND-gate and comprises a firstinput terminal which is connected to the output terminal 44 of thecomparator 41 and a second input terminal. The logic gate 45 is designedas an AND-gate. An output terminal of the logic gate 45 is connected toa control terminal of the fourth switch 46. A controlled section of thefourth switch 46, that is the output circuit of the fourth switch 46,couples the output terminal of the protection circuitry 40 and,therefore, a control terminal 4 of the first switch 3 to the referencepotential terminal 8.

The first transistor 60 couples the control terminal 4 of the firstswitch 3 to a second power supply terminal 9. A control terminal of thefirst transistor 60 is connected to the second terminal 6 of the firstswitch 3. A first terminal of the controlled section of the firsttransistor 60 is connected to the power supply terminal 9 and a secondterminal of the controlled section is connected to the control terminal4 of the first switch 3.

The first, the second, the third and the fourth switch 3, 25, 31, 46 andthe first transistor 60 are each realized as a MOSFET. The first switch3 is realized as a N-channel MOSFET.

A load current Iload flows through the current sensor 10 and the firstswitch 3 to the load 70 and generates a load voltage Vout at the secondterminal 2 of the switch arrangement. A current signal SIL withinformation about the load current Iload is provided by the currentsensor 10 to the second input terminal 23 of the OTA 21 of the firstcontrol circuitry 20 and to the first input terminal 42 of thecomparator 41 of the protection circuitry 40.

A first threshold signal TH1 is applied to the first input terminal 22of the OTA 21. A second mode signal SM2 is provided to a controlterminal of the second switch 25. The first control circuitry 20provides a first signal S1 at the output terminal of the first controlcircuitry 20, wherein the first signal S1 depends on the load currentsignal SIL and the second mode signal SM2.

A first mode signal SM1 is provided to a control terminal of the thirdswitch 31. The current sink 32 provides a current IOFF. The secondcontrol circuitry 30 provides a second signal S2 at the output terminalof the second control circuitry 30 which is equal to the current sinkcurrent IOFF in the case that the third switch 31 is in a closedposition. If the third switch 31 is in an open position, the outputterminal of the second control circuitry 30 is in a high impedancestate.

A second threshold signal TH2 is applied to the second input terminal 43of the comparator 41. A third mode signal SM3 is provided to an inputterminal of the logic gate 45. The protection circuitry 40 provides athird signal S3 at the output terminal of the protection circuitry 40,wherein the third signal S3 depends on the load current signal SIL andthe third mode signal SM3. The first mode signal SM1 is the invertedsignal of the second and the third mode signals SM2, SM3 which areequal.

It is an advantage of the first control circuitry 20 comprising an OTA21 that the first switch 3 can not only be operated in an on-state or anoff-state, but can also be operated in an intermediate-state. The firstswitch 3 has the functionality of a controlled resistor in theintermediate-state.

Other embodiments which can replace the embodiments shown in the FIGS.1, 2 and 3 are common for a person skilled in the art.

For example, in an alternative embodiment, the first control circuitry20 comprises a comparator or a differential amplifier instead of the OTA21.

In an alternative embodiment, the logic gate 45 of the protectioncircuitry 40 is realized as a NAND-Gate which is coupled to the fourthswitch 46 via an inverter.

In another embodiment, the logic gate 45 of the protection circuitry 40is realized as a NOR-Gate to which an alternative third mode signal SM3is provided which is the first mode signal SM1 according to thisembodiment. In this embodiment, the output of the current sensor 10 iscoupled to the second input terminal 43 of the comparator 41 and thesecond threshold signal TH2 is provided to the first input terminal 42of the comparator 41.

FIG. 2 shows an exemplary embodiment of the second control circuitry 30,comprising the current sink 32 and the third switch 31. The current sink32 is realized as a current mirror and comprises a second transistor 33and a third transistor 34. A first terminal of the second transistor 33and a first terminal of the third transistor 34 are connected to thereference potential terminal 8. A second terminal of the secondtransistor 33 is coupled to a control terminal of the second transistor33 and to a control terminal of the third transistor 34. A secondterminal of the third transistor 34 is coupled to the third switch 31which is coupled to the output terminal of the second control circuitry30. When the third switch 31 is closed, the current sink current IOFFflows through the third transistor 34.

FIG. 3 shows an exemplary embodiment of the signals in the switcharrangement according to FIG. 1. The function of the parts of the switcharrangement and the signals are described in detail using FIG. 3. FIG. 3shows the load voltage Vout and the load current Iload. FIG. 3 alsoshows a gate voltage Vgate which is the voltage at the control terminal4 of the first switch 3 and a gate source voltage Vgs which is thevoltage between the control terminal 4 of the first switch 3 and thesecond terminal 6 of the first switch 3. Because the first switch 3 is aN-channel MOSFET according to the switch arrangement shown in FIG. 1,the first terminal 5 of the first switch 3 is a drain terminal and thesecond terminal 6 of the first switch 3 is a source terminal of thefield-effect transistor.

FIG. 3 also shows the second mode signal SM2 which is equal to the thirdmode signal SM3. The second mode signal SM2 is an inverted signal to thefirst mode signal SM1. FIG. 3 further shows a comparator output signalCOUT which is provided by the output terminal 44 of the comparator 41.The different signals are shown versus a time t.

In a first state ST1, the second and the third mode signals SM2, SM3 arein a low-state. Therefore, the second and the fourth switches 25, 46 arein an open state and the output terminals of the first control circuitry20 and of the protection circuitry 40 are in a high-impedance state. Thefirst mode signal SM1 is in a high-state and, therefore, the currentsink current IOFF discharges the capacitance of the control terminal 4of the first switch 3. The gate voltage Vgate at the control terminal 4of the first switch 3 obtains a low value, so that the first switch 3 isin an off-state. The gate voltage Vgate obtains the minimum value whichcan be achieved by the current sink 32. The minimum value of the gatevoltage Vgate is, therefore, limited by the minimum of the supplypotentials which are applied to the current sink 32.

In a second state ST2, the second and the third mode signals SM2, SM3obtain a high-state and the first mode signal SM1 obtains a low-state.Because the load current Iload is smaller than the second thresholdsignal TH2, the output terminal of the protection circuit 40 is in ahigh-impedance state. Because the load current Iload is lower than thefirst threshold signal TH1, the operational transconductance amplifier21 provides a positive current at its output terminal 24 which yields afirst signal S1 with a positive current value. Therefore, the gatevoltage Vgate at the control terminal 4 of the first switch 3 increases.The gate voltage Vgate achieves a maximum value which depends on themaximum value of a voltage which can be provided by the output terminal24 of the operational transconductance amplifier 21. The voltage at theoutput terminal 24 of the OTA 21 is limited by the maximum of the supplypotentials of the operational transconductance amplifier 21.

FIG. 3 shows that the rise of the gate voltage Vgate is performed with afirst time constant τ1. The first time constant τ1 depends on thecapacitance of the control terminal 4 of the first switch 3 and thecurrent value of the first signal S1 which is provided by theoperational transconductance amplifier 21. The first time constant τ1depends on a product of the gate capacitance and of the current value ofthe first signal S1. The switch arrangement, therefore, shows a softstart characteristic. Because of the soft start characteristic a load 70with a high capacitance 72 can be connected to the second terminal 2 anda high in-rush current is avoided. This is provided by the slow changeof the resistance of the controlled section of the first switch 3 froman off-state with a high resistance to an on-state with a lowresistance. A current limitation is not triggered because of this softstart.

In a third state ST3, the second mode signal SM2 is in a high-state. Theload current Iload is greater than the first threshold signal TH1 andthe load current Iload is smaller than the second threshold signal TH2.Therefore, the signal at the first input terminal 22 of the operationaltransconductance amplifier 21 is smaller than the signal at the secondinput terminal 23 of the operational transconductance amplifier 21. Thefirst signal S1, therefore, is a current with a negative sign whichdischarges the control terminal 4 of the first switch 3. The gatevoltage Vgate is reduced so that the load current Iload is equivalent tothe first threshold signal TH1.

In a fourth state ST4, the second and the third mode signal SM2, SM3 arein a high-state. The load current Iload obtains a value which is greaterthan the first threshold signal TH1 and also greater than the secondthreshold signal TH2. This can for example be caused by a sudden shortcircuit in the load 70. The comparator output signal COUT at the outputterminal 44 of the comparator 41 will be changed from a low-state to ahigh-state. The logic gate 45 which is realized as an AND-gate providesa high-state at the output terminal of the logic gate 45 and, therefore,a high-state at the control terminal of the fourth switch 46. Therefore,the controlled section of the fourth switch 46 will be very rapidlyswitched into a low resistance state, so that the control terminal 4 ofthe first switch 3 is very quickly discharged. The gate voltage Vgatedrops to a value so that the first switch 3 is in an off-state. When theload current Iload obtains a small value, the output terminal of theprotection circuitry 40 will be again in a high-impedance state. Theswitch arrangement will start with the soft start characteristics andthe control terminal 4 of the first switch 3 will be charged by thefirst signal S1 provided by the first control circuitry 20 with thefirst time constant τ1.

In a fifth state ST5, a transition from a low-state of the second modesignal SM2 to a high-state is shown. FIG. 3 shows an increase of theload current Iload and of the output voltage Vout with the first timeconstant τ1 of the soft start characteristic described above.

In a sixth state ST6, a transition of the second mode signal SM2 from ahigh-state to a low-state is shown. The voltage Vgate applied to thecontrol terminal 4 of the first switch 3 will be reduced by the secondsignal S2, so that the discharging procedure is performed. This is doneby realizing a second time constant τ2. In an embodiment, the currentsink 32 is realized as a resistor. In this embodiment, the second timeconstant τ2 depends on the product of the gate capacitance and the valueof the resistor. Alternatively, the discharging can be implemented byusing a constant current sink current IOFF, provided by the embodimentof the current sink 32 shown in FIG. 2. Therefore, the switch-offprocedure is also controlled and is relatively slow.

The function of the first transistor 60 is to protect the first switch 3in case that the first switch 3 has a maximum allowed gate sourcevoltage Vgs between the control terminal 4 and the second terminal 6 ofthe first switch 3 which is lower than the maximum of the supplyvoltages. In this case, the first transistor 60 will be switched on fora reduction of the gate voltage Vgate and ensures that the gate sourcevoltage Vgs does not exceed the allowed value for the gate sourcevoltage.

It is an advantage of the switch arrangement according to FIG. 1 that itshows a current limitation capability, a short circuit currentprotection, a soft start characteristic and a soft recovery after ashort circuit event. The time constants τ1, τ2 for the soft startcharacteristic and for the switch-off characteristic can be controlledindependently by the design of the operational transconductanceamplifier 21 in the case of the soft start characteristics and by thedesign of the current sink 32 in case of the switch-off characteristic.

The scope of protection of the invention is not limited to the examplesgiven hereinabove. The invention is embodied in each novelcharacteristic and each combination of characteristics, which includesevery combination of any features which are stated in the claims, evenif this feature or combination of features is not explicitly stated inthe examples.

1. A switch arrangement, comprising: a first and a second terminal; afirst switch comprising: a control terminal, a first terminal which iscoupled to the first terminal of the switch arrangement, and a secondterminal which is coupled to the second terminal of the switcharrangement; a current sensor for the measurement of a load currentflowing through the first switch; a first control circuitry which iscoupled to an output terminal of the current sensor and to the controlterminal of the first switch for providing a first signal to the controlterminal of the first switch for current limitation of the load currentby a first threshold signal, the first control circuitry comprises: anoperational transconductance amplifier having: a first input terminalwhich receives the first threshold signal; a second input terminal whichis coupled to the output terminal of the current sensor; and an outputterminal which is coupled to the control terminal of the first switch; asecond control circuitry which is coupled to the control terminal of thefirst switch for providing a second signal to the control terminal ofthe first switch, wherein the second signal depends on a first modesignal; and a protection circuitry against short circuit which isconnected to the output terminal of the current sensor and couples thecontrol terminal of the first switch to a reference potential terminal,the protection circuitry comprises: a comparator having: a first inputterminal which is coupled to the output terminal of the current sensor;a second input terminal which receives a second threshold signal; and anoutput terminal; and a fourth switch having: a first terminal which iscoupled to the control terminal of the first switch; a second terminalwhich is coupled to the reference potential terminal; and a controlterminal which is coupled to the output terminal of the comparator, theprotection circuitry comprises a logic gate having a first inputterminal which is coupled to the output terminal of the comparator, asecond input terminal which receives a third mode signal, and an outputterminal which is coupled to the control terminal of the fourth switch,wherein a second mode signal and the third mode signal are equalsignals, and the first mode signal is an inverted signal of the secondmode signal, and wherein the logic gate has a function equivalent to anAND-gate.
 2. The switch arrangement according to claim 1, wherein thefirst control circuitry and the second control circuitry are eachrealized as a current source.
 3. The switch arrangement according toclaim 1, wherein the first control circuitry comprises a second switchhaving a control terminal which receives a second mode signal, a firstterminal which is coupled to the output terminal of the operationaltransconductance amplifier, and a second terminal which is coupled tothe control terminal of the first switch.
 4. The switch arrangementaccording to claim 1, wherein the second control circuitry comprises acurrent sink, and a third switch, wherein the third switch comprises acontrol terminal which receives a first mode signal, a first terminalwhich is coupled to the reference potential terminal via the currentsink, and a second terminal which is coupled to the control terminal ofthe first switch.
 5. The switch arrangement according to claim 4,wherein the current sink is realized as a current mirror.
 6. The switcharrangement according to claim 1, wherein the switch arrangementcomprises a first transistor having a first terminal which is coupled tothe control terminal of the first switch, a second terminal which iscoupled to a supply voltage terminal, and a control terminal which iscoupled to the second terminal of the first switch.
 7. The switcharrangement according to claim 1, wherein the first switch is realizedas a metal-oxide-semiconductor field-effect transistor.
 8. Thearrangement according to claim 1, comprising a load which is coupled tothe second terminal of the switch arrangement.
 9. A method forelectrical switching, comprising controlling a first switch with thesteps of: coupling the first switch via a first transistor to a powersupply terminal, wherein a control terminal of the first transistor isconnected to a terminal of the first switch; providing a first signal toa control terminal of the first switch depending on a load current whichflows through the first switch and through a current sensor, wherein thefirst signal is provided by a first control circuit in such a way thatthe load current is smaller or is equal to a first threshold signal;providing a second signal to the control terminal of the first switchdepending on a first mode signal; and providing a third signal by aprotection circuit that couples the control terminal of the first switchto a reference potential terminal for protection against short circuitto the control terminal of the first switch depending on the loadcurrent and a second threshold signal, wherein an output of the currentsensor is connected to the first control circuit and to the protectioncircuit.
 10. The method according to claim 9, wherein the second signalis a current having only one sign and wherein the first signal is acurrent having a sign depending whether the load current has a greateror a smaller value in comparison to the first threshold signal.
 11. Aswitch arrangement, comprising: a first and a second terminal; a firstswitch comprising: a control terminal, a first terminal which is coupledto the first terminal of the switch arrangement, and a second terminalwhich is coupled to the second terminal of the switch arrangement; acurrent sensor for the measurement of a load current flowing through thefirst switch; a first control circuitry which is coupled to an outputterminal of the current sensor and to the control terminal of the firstswitch for providing a first signal to the control terminal of the firstswitch for current limitation of the load current by a first thresholdsignal; a second control circuitry which is coupled to the controlterminal of the first switch for providing a second signal to thecontrol terminal of the first switch, wherein the second signal dependson a first mode signal; a protection circuitry against short circuitwhich is connected to the output terminal of the current sensor andcouples the control terminal of the first switch to a referencepotential terminal; and a first transistor having: a first terminalwhich is coupled to the control terminal of the first switch; a secondterminal which is coupled to a supply voltage terminal; and a controlterminal which is coupled to the second terminal of the first switch.12. A switch arrangement, comprising: a first and a second terminal; afirst switch comprising: a control terminal, a first terminal which iscoupled to the first terminal of the switch arrangement, and a secondterminal which is coupled to the second terminal of the switcharrangement; a current sensor for the measurement of a load currentflowing through the first switch; a first control circuitry which iscoupled to an output terminal of the current sensor and to the controlterminal of the first switch for providing a first signal to the controlterminal of the first switch for current limitation of the load currentby a first threshold signal, the first control circuitry comprises: anoperational transconductance amplifier having: a first input terminalwhich receives the first threshold signal; a second input terminal whichis coupled to the output terminal of the current sensor; and an outputterminal which is coupled to the control terminal of the first switch; asecond control circuitry which is coupled to the control terminal of thefirst switch for providing a second signal to the control terminal ofthe first switch, wherein the second signal depends on a first modesignal; and a protection circuitry against short circuit which isconnected to the output terminal of the current sensor and couples thecontrol terminal of the first switch to a reference potential terminal,the protection circuitry comprises: a comparator having: a first inputterminal which is coupled to the output terminal of the current sensor;a second input terminal which receives a second threshold signal; and anoutput terminal; and a fourth switch having: a first terminal which iscoupled to the control terminal of the first switch; a second terminalwhich is coupled to the reference potential terminal; and a controlterminal which is coupled to the output terminal of the comparator, theprotection circuitry comprises a logic gate having a first inputterminal which is coupled to the output terminal of the comparator, asecond input terminal which receives a third mode signal, and an outputterminal which is coupled to the control terminal of the fourth switch,wherein the first mode signal and the third mode signal are equalsignals, and the first mode signal is an inverted signal of a secondmode signal, and wherein the logic gate has a function equivalent to aNOR-gate.